The present invention relates to a rack steering system for motor vehicles with a guide and support unit displaceably supporting the rack at its end sections and with inner (i.e. remote from the wheels) track rod joints offset transverse to the longitudinal axis of the rack. The track rod joints are arranged on the free ends of two deflection levers, which are arranged at both sides of the guide and support unit and are drive-connected to the rack. The deflection levers can be pivoted about support pins directed transverse to the longitudinal axis of the rack.
EP 04 81 622 A1 describes a rack steering system. The offset arrangement of the inner track rod joints relative to the longitudinal axis of the rack is necessary or advantageous if a rack steering system has to be arranged under restricted conditions, such as are typically present in the region of the front axle in present-day passenger cars, in particular where the vehicle engine extends in the longitudinal direction between the front wheels. In this case, the rack must usually be arranged under the oil sump or the bottom of the engine. As a rule, however, such a low-level arrangement of the inner track rod joints is not possible or desirable because the necessary free movement between the track rods and the transverse links of the front wheels is not available or the result is kinematically unfavorable positions of the track rods.
The known rack steering system described in EP 04 81 622 A1 provides for end pieces which are arranged on the rack and which are displaceably guided in associated end parts of the guide and support unit to engage, via trunnions or the like arranged thereon, in elongated holes of the deflection levers such that a drive connection configured in the manner of a sliding joint is formed between the rack and the deflection levers. Such a configuration is relatively complicated and offers only little freedom with respect to the arrangement of the deflection levers.
It is, therefore, an object of the present invention to provide a particularly useful construction for a rack steering system of the above-mentioned type.
This object has been achieved in accordance with the present invention in that the deflection levers are drive-connected to a central tap-off connection of the rack by connecting struts hinged at their free ends. The deflection levers can be arranged in various ways on the guide and support unit. It is, in particular, possible to arrange the deflection levers on the mutually facing sides of end holding features (e.g., flanges) for fastening the guide and support unit.
In accordance with one presently preferred embodiment of the invention, the central tap-off connection, the hinge points of the connecting struts on the central tap-off connection and the connecting joints between the connecting struts and the deflection levers can be fitted in a plane containing the longitudinal axis of the rack. Consequently, torques acting on the rack relative to its longitudinal axis are completely avoided. The rack steering system of the present invention thus correspondingly retains ease of movement without great complication in the rack support arrangements.
In a particularly advantageous embodiment of the present invention, the connecting struts are hinged on the central tap-off connection at a transverse distance from the longitudinal axis of the rack so that the virtual extensions of the connecting struts pass through rack supports arranged on both sides of the central tap-off connection on or in the guide and support unit near the longitudinal axis of the rack. This feature permits particularly low loading on the rack supports to be achieved.